Each of these behaviors may not be illegal individually and each behavior may not constitute stalking. Often, stalkers plan their actions to not be drastic or illegal so they are less likely to be reported. However, a pattern of incidents causing the victim fear or annoyance may constitute stalking.
Any of the above mentioned behaviors performed via the internet may also fall under the definition of "cyber-stalking" and are also illegal. If you are wondering where to draw the line between secret admirer and stalker, consider if the attention you are receiving is unwanted or if you feel afraid, paranoid, or intimidated.